Within the context of the global climate discussion, the rules concerning the energy efficiency and CO2 emissions of internal combustion engines have already been tightened, and in the future, even stricter regulations are to be expected. This is why increased efforts have been made for some time to use the exhaust gas heat of internal combustion engines, possibly during the entire engine operation, and preferably to convert it into electric energy. With this electric energy, it is then, for example, possible to charge accumulators or to operate electric devices. So-called “thermoelectric generator modules” (referred to as TEG modules below) which convert thermal energy into electric energy, and which can be used in exhaust systems, are already described in the prior art.
Such a device for exhaust gas heat utilization by means of TEG modules is for example disclosed in document DE 10 2009 025 033 A1. Furthermore, the common structure and the general operating principle of TEG modules are already sufficiently known from this document and from several further publications in the prior art, such that they are not discussed in more detail.
A great challenge in TEG modules is the efficient transfer of heat, i.e. a transfer of heat which loses as little heat as possible between the heat source, for example the hot exhaust gas, or the heat sink, for example a cooling agent, and the thermoelectrically active materials of the TEG module. The TEG module is delimited both on the “hot side” and on the “cold side” by a respective cover layer which is made of ceramics, for example, and adjoins an exhaust gas line or a cooling agent line. To realize a constantly high heat transmission between the cover layers and the exhaust gas line or the cooling agent line, the involved assemblies are compressed under high pressure and are then braced.
There is a need to provide a device for exhaust gas heat utilization in internal combustion engines, the design of which ensures with low manufacturing expenditure a lasting good transfer of heat, and thus a high overall efficiency of the device.